Origin

Mad Jack

The two having shared a cell in prison together, Berkhart was trained in arts of illusion by the original Mysterio himself. While Quentin Beck had faked his death, Berkhart was hired by J. Jonah Jameson to convince Spider-Man that Berkhart was the Ghost of Mysterio. With Maguire's assistance, took up the mantle of the Jack O'Lantern (preferring to call himself "Mad Jack" to differentiate himself from the others to have taken up that role). Several years later, Mysterio did die for real and Berkhart decided to take on the role of Mysterio on a full-time basis with Mysterio's cousin Maguire providing tech support. As Mysterio, Berkhart battled Spider-Man and joined the Sandman' s Sinister Six.

Creation

The character was created by Gerry Conway and Ross Andru and first appeared in The Amazing Spider-Man #141. The character was brought back over 20 years later when Mysterio died for real, although his return was mostly just to excuse editor incompetence in Mysterio continuing to appear despite his death.

Major Story Arcs

Media Blizzard

Berkhart hired a certain villain by the name of Armada to steal a revelutionary new D.I.T (Digital Imagery Transmission) chip, which can emit thoughts as holographic images. He buys a TV station as Randolph Hines and turning it into an overnight sensation by hypnotizing his viewers into "MysteryVision" addicted zombies.

I Hate a Mystery (Civil War)

He was last seen teaming up with Spider-Man to battle Francis Klum who had also started calling himself Mysterio. This led to the confrontation between both men as well as the demonic spirit of the original Mysterio. Whereas Klum possibly died and the original Mysterio eventually returned, Berkhart hasn't been seen since.